Doctors for paper and like machines



June 13, 1961 H. E. B. SCOTT 2,987,748

DOCTORS FOR PAPER AND LIKE MACHINES Filed April 2. 1959 Unite Statesatent 2,987 748 DOCTORS FOR PAPER AND LIKE MACHINES Harold Eric BaliolScott, Heath, Weybridge, England, assignor to Vickerys Limited, London,England Filed Apr. 2, 1959, Ser. No. 803,693 Claims priority,application Great Britain June 9, 1958 12 Claims. (Cl. 15-256.5)

front, i.e. from the side of the holder nearer the roll. The i holder isnormally carried, in use of the doctor, on a support which is biased bya spring, by gravity or by fluid pressure so that the blade bears on thesurface of the roll to be dootored, the support being capable of rockingmovement to enable the doctor blade to be lifted off the roll.Especially when the blade is so mounted that, when in service, itextends in a downward direction it must be prevented from falling out ofthe holder when it is lifted off the roll, as otherwise there would beserious risk of injury to personnel and of damage to the plant to bdoctored.

It has hitherto been the practice to provide on the underside of thedoctor blade, the expression underside being used herein to designatethe side of the doctor blade nearer the roll, rivets or otherprojections which engage in a longitudinal slot in the holder, the lipconstituting the front of the slot being formed with gaps through whichthe rivets may be passed for the purpose of introducing the blade into,or withdrawing it from, the holder and the blade being slid endwise,preparatory to placing the doctor in service, to bring the rivets out ofregister with the gaps. Difiiculty, however, is often experienced inremoving the blade fromthe holder after a period of service owing todirt accumulated in the slot in the holder obstructing the endwisemovement of the blade in the holder required to bring the rivets backinto engagement with the gaps. It is the object of this invention toobviate this disadvantage. The invention provides a doctor for the rollsof paper making or like machines, comprising a doctor blade and anelongated holder supporting the rear edge of the doctor blade, the bladebeing normally retained against forward a withdrawal from the holder byspring tongues provided,

either on the rear edge of the blade and engaging a longitudinal groovein the holder, or on a member retained in the holder and engaging alongitudinal groove in the blade, said blade being capable in eithercase after it has been lifted off the roll, of limited rocking movementin relation to the holder to disengage the spring tongues from thegroove and to permit of forward withdrawal of the blade from the holder.

Where the blade is of thin metal, the spring tongues are preferablydownwardly bent at intervals along the rear edge of the blade and engagein alongitudin'al' groove in the holder beneath the blade.

Where, however, the blade is of thick non-metallic material, alongitudinal groove is providedin the blade near its rear edge andpreferably on its upper surface for cooperation with spring tongues onthe forward edge of a keep plate retained in the holder.

A general object of this invention is to provide doctors which arereliable and safe'in operation and which permit safe and easy removal ofthe blade for servicing.

Another object of the invention is to provide a doctor Patented June 13,1961 ice in which a single holder is capable of holding blades of verydiflierent thicknesses.

A further object of the invention is to provide a doctor in which thesame holder is capable of retaining ditferen types of blades by the useof an adaptor.

Other objects and advantages of the invention will be come apparent andthe invention will be fully understood from the following descriptionand the accompanying drawing, in which: Y

FIG. 1 is a side elevation of one embodiment of the invention; Y 1 1FIG. 2 is a partial underside plan view of the keep plate of the doctorshown in FIG. 1;

FIG. 3 is a side elevation of a second embodiment; and

FIG. 4 is a partial underside planview of the blade of the doctor shownin FIG. 3.

Like reference numerals indicate like parts throughout the figures.

Both forms of doctor shown in the drawings are of the general characterdescribed in British Patent No. 7 52,098 and US. application Serial No.475,083, the holder being constituted by upper and lower parts 10, 11suitably at tached together, as in the above-mentioned patent, forexample. The lower part 10 of the holder is formed near the front with alongitudinal groove 12 extending throughout its length.

In the construction shown in FIGS. 1 and 2 the blade 13 is of thicknon-metallic material while in the other construction the blade 113 isof thin metal. In both cases, a pressure plate 14 bears against theblade for it's full length, and a keep plate 15 situated below thepressure plate overlies the rear edge of the plate and providesclearance permitting the blade to float. The forward edge of the keepplate 15 is bevelled as shown at 16." The pres sure plate 14 has aseries of downwardly depending retaining projections 24 which extendthrough holes inthe keep plate into a longitudinal slot 25 in theholder.

In the case of the doctor shown in FIGS. 1 and 2 the blade 13 has alongitudinal groove 17 in its upper surface situated near its rear edgeand extending for its full length. The forward edge of the keep plate 15is formed at intervals, e.g. of 3, 4 or 5 feet, with cutaway portions 18between each pair of which is situated a downwardly bent spring tongue19. These spring tongues 19 extend downwardly into the groove 17 in theblade, as shownfso as to restrain the blade against forward withdrawalfrom the holder. When, however, the doctor has been withdrawn from theroll, it can be rocked about the upper end of the lip 20 on the holderwhich constitutes the front of the groove 12 and against the pressureexerted by the pressure plate 14 and the spring tongues of the keepplate 15, sufficiently to disengage the tongues 19 from the groove 17and allow the blade to be withdrawn forwardly from the holder. The rearedge of the blade is bevelled at 21 on its upper surface to assist thepassage of the blade into the holder past the tongues 19 when the bladeis inserted into the holder. 7

In the doctor shown in FIGS. 3 and 4, cutaway portions 118 are formed atintervals in the rear edge of the blade 113, a downwardly bent springtongue 119 being provided between each pair of cutaway portions. Thstongues 119 engage in the groove 12 so as normally to prevent the bladefrom being withdrawn forwardly from the holder. The blade 113 can,however, be rocked about the lip 20 and against the pressure exerted bythe pressure plate 14 and the spring tongues of the blade to disengagethe tongues 119'from the groove 12. i The keep plate 15 in this case hasnospring tongues at its forward edge.

It is often necessary to use blades of a different thickness or materialwhen a change :is made in the product being manufactured or whenthe-roll to 'bedoctord is replaced by one of a different material orhardness. This usually necessitates replacing the complete blade holderby one which is suitable for the new blade. Also, in some border-linecases, it is ditficult to predict whether a thin metal blade or a thickcomposition blade will give the most satisfactory results, and to changethe blade holder is a long and costly matter and can only be done duringthe week-end when the paper machine is shut down.

Provision for overcoming these difliculties is made in the doctoraccording to the invention by reason of the fact that the groove 12 inthe holder has a wide bottom and a narrow top, being of dovetail shape.When a thick composition blade 13 is to be replaced by a thin metalblade 113, the exchange can be made utilizing the same blade holder byinserting a dovetailed make-up piece 26 endwise into the groove 12, theupper portion 27 of which is of thickness appropriate to make up for thedifference in thickness between thick and thin blades.

With this arrangement once the blade holder has been fitted to thedoctor beam or support and lined up true with the roll, either thickcomposition blades with retaining grooves and a cooperating keep platewith spring tongues can be fitted or thin blades with spring retainingtongues and a plain keep plate can be used after the dovetailed make-uppiece has been fitted in position. This change can be made in a veryshort time merely by sliding out the parts not required and replacingthem with alternatives without affecting the alignment of the doctorwith the roll. Various thicknesses of the blade can be used by providinga series of dovetailed pieces of varying height.

The advantage of this arrangement is that there is no need to keep amultiplicity of heavy extruded sections of blade holder in stock toaccommodate blades of different thicknesses. One pair of blade holdersections, with the requisite number of light dovetailed pieces, is allthat is required.

The groove 12 and make-up piece 26 need not necessarily be of dovetailsection. Any other convenient undercut section can be used, provided themake-up piece is prevented from lifting out of the groove. The make-uppiece need not be continuous but can consist of several short lengthsbutted together.

The blade may have a feed-in rivet 28 projecting from its undersurfaceat one end and near its rear edge. This assists in endwise feeding ofthe blade into the holder in applications, e.g. to drying cylinders of apaper machine, where it is impossible to insert the blade into theholder from the front. It is also useful for forward feeding into theholder of very long blades which otherwise require the services ofseveral men spaced along the length of the blade. With the feed-inrivet, only one man is required. He just hooks the rivet into the groove12 in the holder. This holds one end of the blade in position and theworkman can then move along the blade fitting it into position bit bybit.

To remove the blade forwardly, it is first slid endwise by about 1 inchuntil the rivet is disengaged from the groove 12 and the blade can beshaken, while applying a forward pull, until it comes clear of theholder.

It will be appreciated that the spring tongues, whether they areprovided on the blade or on the keep plate, do not positively retain theblade in position in the holder but are able to yield, when the blade isclear of the roll and is rocked sufficiently in relation to the holder,to permit of forward removal of the blade.

While I have shown and described two particular embodiments of myinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from my invention and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim is:

1. A doctor for a roll of-a papermaking or like machine, comprising adoctor blade elongated in a direction parallel to the axis of the rolland having a forward edge adapted to engage the roll and a rear edgeremote from the roll, and an elongated holder in engagement with andsupporting the rear edge of the blade and having a longitudinal groovebeneath the rear end of the blade, the blade having spaced downwardlybent spring tongues at its rear edge which extend into and engage insaid longi-- tudinal groove, a pressure plate disposed above the blade,projecting forwardly from the holder, having its rear edge retained inthe holder and bearing against the upper surface of the blade throughoutsubstantially the whole of its length at a region of said upper surfaceintermediate the front and rear edges of the blade, and a keep platedisposed beneath the pressure plate and projecting forwardly over thegroove, the spring tongues normally cooperating with the groove toprevent forward withdrawal of the blade from the holder but beingdisengageable from the groove by rocking the blade about a longitudinalaxis thereof when the blade has been lifted off the roll.

2. A doctor according to claim 1 wherein the blade has a downwardlyextending feed-in rivet at one end near its rear edge for engagementwith the longitudinal groove in the holder.

3. A doctor according to claim 1 wherein said blade is a thin metalblade and the holder has a longitudinal groove and a grooved make-uppiece having a crosssection corresponding to that of said longitudinalgroove in the holder, to permit the holder to accommodate said thinmetal blade, said spring tongues being in engagement with the groove inthe make-up piece, the make-up piece being shaped so as to be removablefrom the groove in an endwise direction but not upwardly.

4. A doctor according to claim 3, wherein the longitudinal groove of theholder is of dovetail cross-section.

5. A doctor according to claim 3, wherein the blade has a feed-in rivetat one end near its rear edge for engagement with the longitudinalgroove in the holder.

6. A doctor for a roll of a papermaking or like machine, comprising athick non-metallic doctor blade elongated in a direction parallel to theaxis of the roll and having a forward edge adapted to engage the rolland a rear edge remote from the roll, said blade having a longitudinalgroove in its upper surface near its rear edge, an elongated bladeholder supporting the rear edge of the blade, a pressure plate disposedabove the blade, projecting forwardly from the holder, having its rearedge retained in the holder and bearing against the upper surface of theblade throughout substantially the whole of its length, and a keep platedisposed beneath the pressure plate and projecting forwardly over thegroove and having at its forward edge spaced, downwardly bent springtongues engaging the groove in the blade, the spring tongues normallycooperating with the groove to prevent forward withdrawal of the bladefrom the holder but bein disengageable from the groove by rocking theblade about a longitudinal axis thereof when the blade has been liftedoff the roll.

7. A doctor for a roll of a papermaking or like machine, comprising adoctor blade having an elongated width in a direction parallel to theaxis of the roll and having a forward edge adapted to engage the rolland a rear edge remote from the roll, and an elongated blade holder inengagement with and supporting the rear edge of the blade, the blade andholder having retaining means including a groove and a plurality ofspring tongues which are disposed along the width of the blade andinclined to the plane of the blade and engaging the groove to retain theblade against forward withdrawal from the holder when the blade is inits normal roll-engaging position in relation to the holder, theretaining means and holder enabling the blade to have a limited rockingmovement in relation to the holder about a line parallel to the edges ofthe blade to disengage the spring tongues from the groove and therebypermit forward withdrawal of the blade from the holder.

8. A doctor for a roll of a papermaking or like machine, comprising adoctor blade having an elongated width in a direction parallel to theaxis of the roll and having a forward edge adapted to engage the rolland a rear edge remote from the roll, and a blade holder in engagementwith and supporting the blade along a line thereof parallel and close toits rear edge, said blade and bolder including retaining means includinga groove and a pluraltiy of spring tongues located between said line andsaid rear edge, said spring tongues being disposed along the Width ofthe blade and inclined to the plane of the blade and extending into andengaging said groove, said retaining means holding said blade to enableit to rock about a line parallel to said line of support, the springtongues normally cooperating with the groove to prevent forwardwithdrawal of the blade from the holder but being disengageable from thegroove by rocking the blade when the blade has been lifted off the roll.

9. A doctor according to claim 8, including a pressure plate disposedabove the blade and inclined at an angle thereto, means for fasteningsaid pressure plate to said holder, said pressure plate extendingforwardly from the holder into engagement with the blade along a linethereof parallel to said edges and between said line of support and theforward edge of the blade.

10. A doctor for a roll of a papermaking or like machine comprising ablade elongated in the direction parallel to the axis of the roll andhaving a forward edge adapted to engage the roll and a rear edge remotefrom the roll, said blade having a groove in its upper surface near itsrear edge, a blade holder engaging the bottom of the rear of the bladeand supporting the same, a pressure plate disposed above the blade andinclined at an angle thereto, means for fastening the pressure plate tothe holder with the pressure plate extending forwardly b from the holderand engaging and bearing against the upper surface of the blade along aline thereof located forwardly of the holder, means fastened to theholder including a plurality of downwardly bent spring tongues disposedalong the width of the blade and engaging the groove in the blade fornormally preventing forward withdrawal of the blade from the holder butenabling a rocking of the blade when the blade has been lifted off theroll for enabling the blade to be disengaged from the holder.

11. A doctor for a roll of a papermaking or like machine, comprising a'doctor blade elongated in a direction parallel to the axis of the rolland having a forward edge adapted to engage the roll and a rear edgeremote from the roll, and an elongated holder in engagement with andsupporting the rear edge of the blade and having a longitudinal groovebeneath the rear end of the blade, the

blade having spaced downwardly bent spring tongues at its rear edgewhich extend into and engage in said longitudinal groove, a pressureplate disposed above the blade, projecting forwardly from the holder,having its rear edge retained in the holder and bearing against theupper surface of the blade throughout substantially the whole of itslength at a region of said upper surface intermediate the front and rearedges of the blade, the spring tongues normally cooperating with thegroove to prevent forward withdrawal of the blade from the holder butbeing disengageable from the groove by rocking the blade about alongitudinal axis thereof when the blade has been lifted off the roll.

12. A doctor according to claim 11, wherein said blade has a pluralityof pairs of cutaway portions spaced at intervals along the rear edge ofthe blade, each of said tonguees being located between a pair of cutawayportions.

References Cited in the file of this patent UNITED STATES PATENTS2,498,213 Ljungquist Feb. 21, 1950

